Impact of human disturbance on the abundance of non-breeding shorebirds in a subtropical wetland

Shorebird populations have declined due to several threats throughout
their annual cycle. Anthropogenic disturbance is one of the most
ubiquitous threats to shorebird conservation in North America. Here, we
studied the influence of human disturbance on shorebird community dynamics
during migration and winter in Ensenada de La Paz, a subtropical coastal
wetland in Mexico. We used negative binomial generalized linear mixed
models to investigate the associations between spatial, biological, and
anthropogenic variation and local shorebird abundance that accounted for
shorebird body size (small, medium, and large) and foraging strategy
(visual and tactile) of 21 shorebird species. After controlling for these
different correlates of abundance, human disturbance (people, vehicles,
and dogs) was negatively associated with shorebird abundance. During
winter, all shorebird species were negatively related to human disturbance
but positively associated with presence of raptors. However, small,
tactile foraging birds exhibited a proportionally larger negative response
to human disturbance than other shorebird types, indicative of guild-level
sensitivities to human disturbance regimes. The positive association
between shorebird abundance and disturbance from predators was unexpected.
Shorebirds likely concentrate in large groups to reduce predation risk,
resulting in higher densities of shorebirds occurring in areas with high
predation risk. Understanding factors influencing the abundance and
habitat use of shorebirds on their non-breeding grounds is paramount to
support management and conservation policies for shorebirds and their
habitats.